This Core will provide advice, vectors, and as needed actual vector construction and validation for the production of needed knockin and BAC Tg mice. It will also provide initial validation and breeding of such mice, and will transfer mice as needed to the individual projects. However, it will not generally be a mouse- breeding repository. Finally, the Core will provide access to and advice on mouse SNP genotyping which will allow the projects to appropriately conduct "speed-congenic" type backcrossing programs. This in turn will make new strains ready for use much more quickly, thus improving the efficiency ofthe projects overall. It will also provide important quality control over the genetic content ofthe strains used in the project. RELEVANCE (See instructions): This Core will provide important support for genetic experiments that will help elucidate how lupus develops in live animals, which is the only good model for human lupus.